/*
 * Radiotap parser
 *
 * Copyright 2007		Andy Green <andy@warmcat.com>
 * Copyright 2009		Johannes Berg <johannes@sipsolutions.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of ISC
 * license, see COPYING for more details.
 */


#include "platform.h"
#include "radiotap_iter.h"



/* 
 * Function prototypes and related defs are in radiotap_iter.h 
 */
static const struct radiotap_align_size rtap_namespace_sizes[] = {
    [IEEE80211_RADIOTAP_TSFT] = {
        .align = 8,
        .size = 8,
    },
    [IEEE80211_RADIOTAP_FLAGS] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_RATE] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_CHANNEL] = {
        .align = 2,
        .size = 4,
    },
    [IEEE80211_RADIOTAP_FHSS] = {
        .align = 2,
        .size = 2,
    },
    [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_DBM_ANTNOISE] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_LOCK_QUALITY] = {
        .align = 2,
        .size = 2,
    },
    [IEEE80211_RADIOTAP_TX_ATTENUATION] = {
        .align = 2,
        .size = 2,
    },
    [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = {
        .align = 2,
        .size = 2,
    },
    [IEEE80211_RADIOTAP_DBM_TX_POWER] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_ANTENNA] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_DB_ANTNOISE] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_RX_FLAGS] = {
        .align = 2,
        .size = 2,
    },
    [IEEE80211_RADIOTAP_TX_FLAGS] = {
        .align = 2,
        .size = 2,
    },
    [IEEE80211_RADIOTAP_RTS_RETRIES] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_DATA_RETRIES] = {
        .align = 1,
        .size = 1,
    },
    [IEEE80211_RADIOTAP_MCS] = {
        .align = 1,
        .size = 3,
    },
    [IEEE80211_RADIOTAP_AMPDU_STATUS] = {
        .align = 4,
        .size = 8,
    },
    [IEEE80211_RADIOTAP_VHT] = {
        .align = 2,
        .size = 12,
    },
    [IEEE80211_RADIOTAP_TIMESTAMP] = {
        .align = 8,
        .size = 12,
    },
    /*
     * Add more here as they are defined in radiotap.h
     */
};



static const struct ieee80211_radiotap_namespace radiotap_ns = {
    .n_bits = sizeof(rtap_namespace_sizes) / sizeof(rtap_namespace_sizes[0]),
    .align_size = rtap_namespace_sizes,
};



/**
 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
 * 
 * @iterator: radiotap_iterator to initialize
 * 
 * @radiotap_header: radiotap header to parse
 * 
 * @max_length: total length we can parse into (eg, whole packet length)
 *
 * Returns: 0 or a negative error code if there is a problem.
 *
 * This function initializes an opaque iterator struct which can then
 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
 * argument which is present in the header.  It knows about extended
 * present headers and handles them.
 *
 * How to use:
 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
 * checking for a good 0 return code.  Then loop calling
 * __ieee80211_radiotap_iterator_next()... it returns either 0,
 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
 * The iterator's @this_arg member points to the start of the argument
 * associated with the current argument index that is present, which can be
 * found in the iterator's @this_arg_index member.  This arg index corresponds
 * to the IEEE80211_RADIOTAP_... defines.
 *
 * Radiotap header length:
 * You can find the CPU-endian total radiotap header length in
 * iterator->max_length after executing ieee80211_radiotap_iterator_init()
 * successfully.
 *
 * Alignment Gotcha:
 * You must take care when dereferencing iterator.this_arg
 * for multibyte types... the pointer is not aligned.  Use
 * get_unaligned((type *)iterator.this_arg) to dereference
 * iterator.this_arg for type "type" safely on all arches.
 *
 * Example code: parse.c
 */

int ieee80211_radiotap_iterator_init(struct ieee80211_radiotap_iterator *iterator,
                                     struct ieee80211_radiotap_header *radiotap_header,
                                     int max_length, 
                                     const struct ieee80211_radiotap_vendor_namespaces *vns) {
    /* 
     * Must at least have the radiotap header 
     */
    if (max_length < (int)sizeof(struct ieee80211_radiotap_header)) {
        return -EINVAL;
    }


    /* 
     * Linux only supports version 0 radiotap format 
     *
     */
    if (radiotap_header->it_version) {
        return -EINVAL;
    }


    /* 
     * Sanity check for allowed length and radiotap length field 
     *
     */
    if (max_length < get_unaligned_le16(&radiotap_header->it_len)) {
        return -EINVAL;
    }


    iterator->_rtheader = radiotap_header;
    iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
    iterator->_arg_index = 0;
    iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
    iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
    iterator->_reset_on_ext = 0;
    iterator->_next_bitmap = &radiotap_header->it_present;
    iterator->_next_bitmap++;
    iterator->_vns = vns;
    iterator->current_namespace = &radiotap_ns;
    iterator->is_radiotap_ns = 1;

    #ifdef RADIOTAP_SUPPORT_OVERRIDES
    iterator->n_overrides = 0;
    iterator->overrides = NULL;
    #endif



    /* 
     * Find payload start allowing for extended bitmap(s) 
     */
    if (iterator->_bitmap_shifter & (1 << IEEE80211_RADIOTAP_EXT)) {
        if ((unsigned long)iterator->_arg - (unsigned long)iterator->_rtheader + sizeof(uint32_t) > (unsigned long)iterator->_max_length) {
            return -EINVAL;
        }


        while (get_unaligned_le32(iterator->_arg) & (1 << IEEE80211_RADIOTAP_EXT)) {
            iterator->_arg += sizeof(uint32_t);

            /*
             * Check for insanity where the present bitmaps keep claiming to extend up to or even 
             * beyond the stated radiotap header length
             */

            if ((unsigned long)iterator->_arg - (unsigned long)iterator->_rtheader + sizeof(uint32_t) > (unsigned long)iterator->_max_length) {
                return -EINVAL;
            }
        }



        iterator->_arg += sizeof(uint32_t);

        /*
         * No need to check again for blowing past stated radiotap header length, because 
         * ieee80211_radiotap_iterator_next checks it before it is dereferenced
         */
    }



    iterator->this_arg = iterator->_arg;


    /* 
     * We are all initialized happily 
     */
    return 0;
}



static void find_ns(struct ieee80211_radiotap_iterator *iterator,
                    uint32_t oui, 
                    uint8_t subns) {
    int i;

    iterator->current_namespace = NULL;

    if (!iterator->_vns) {
        return;
    }

    for (i = 0; i < iterator->_vns->n_ns; i++) {
        if (iterator->_vns->ns[i].oui != oui) {
            continue;
        }
        
        if (iterator->_vns->ns[i].subns != subns) {
            continue;
        }

        iterator->current_namespace = &iterator->_vns->ns[i];

        break;
    }
}



#ifdef RADIOTAP_SUPPORT_OVERRIDES
static int find_override(struct ieee80211_radiotap_iterator *iterator,
                         int *align, 
                         int *size) {
    int i;

    if (!iterator->overrides) {
        return 0;
    }

    for (i = 0; i < iterator->n_overrides; i++) {
        if (iterator->_arg_index == iterator->overrides[i].field) {
            *align = iterator->overrides[i].align;
            *size = iterator->overrides[i].size;

            if (!*align) {
                /* 
                 * Erroneous override 
                 */
                return 0;
            }
            return 1;
        }
    }

    return 0;
}
#endif




/**
 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
 * 
 * @iterator: radiotap_iterator to move to next arg (if any)
 *
 * Returns: 0 if there is an argument to handle,
 * -ENOENT if there are no more args or -EINVAL
 * if there is something else wrong.
 *
 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
 * in @this_arg_index and sets @this_arg to point to the
 * payload for the field.  It takes care of alignment handling and extended
 * present fields.  @this_arg can be changed by the caller (eg,
 * incremented to move inside a compound argument like
 * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
 * little-endian format whatever the endianness of your CPU.
 *
 * Alignment Gotcha:
 * You must take care when dereferencing iterator.this_arg
 * for multibyte types... the pointer is not aligned.  Use
 * get_unaligned((type *)iterator.this_arg) to dereference
 * iterator.this_arg for type "type" safely on all arches.
 */

int ieee80211_radiotap_iterator_next(struct ieee80211_radiotap_iterator *iterator) {
    
    while (1) {
        int hit = 0;
        int pad, align, size, subns;
        uint32_t oui;


        /* 
         * If no more EXT bits, that's it
         */
        if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT && !(iterator->_bitmap_shifter & 1)) {
            return -ENOENT;
        }


        if (!(iterator->_bitmap_shifter & 1)) {
            /*
             * Arg not present
             */
            goto next_entry; 
        }



        /* 
         * Get alignment/size of data 
         */
        switch (iterator->_arg_index % 32) {
            case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
            case IEEE80211_RADIOTAP_EXT:
                align = 1;
                size = 0;
                break;
            case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
                align = 2;
                size = 6;
                break;
            default:
                #ifdef RADIOTAP_SUPPORT_OVERRIDES
                if (find_override(iterator, &align, &size)) {
                    /* 
                     * All set 
                     */
                } 
                else
                #endif
                if (!iterator->current_namespace || iterator->_arg_index >= iterator->current_namespace->n_bits) {
                    if (iterator->current_namespace == &radiotap_ns) {
                        return -ENOENT;
                    }

                    align = 0;
                } else {
                    align = iterator->current_namespace->align_size[iterator->_arg_index].align;
                    size = iterator->current_namespace->align_size[iterator->_arg_index].size;
                }


                if (!align) {
                    /* 
                     * Skip all subsequent data 
                     * 
                     */
                    iterator->_arg = iterator->_next_ns_data;

                    /* 
                     * Give up on this namespace 
                     * 
                     */
                    iterator->current_namespace = NULL;

                    goto next_entry;
                }

                break;
        }

        /*
         * Arg is present, account for alignment padding
         *
         * Note that these alignments are relative to the start
         * of the radiotap header.  There is no guarantee
         * that the radiotap header itself is aligned on any
         * kind of boundary.
         *
         * The above is why get_unaligned() is used to dereference
         * multibyte elements from the radiotap area.
         */

        pad = ((unsigned long)iterator->_arg - (unsigned long)iterator->_rtheader) & (align - 1);

        if (pad) {
            iterator->_arg += align - pad;
        }

        if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
            int vnslen;

            if ((unsigned long)iterator->_arg + size - (unsigned long)iterator->_rtheader > (unsigned long)iterator->_max_length) {
                return -EINVAL;
            }

            oui = (*iterator->_arg << 16) | (*(iterator->_arg + 1) << 8) | *(iterator->_arg + 2);
            
            subns = *(iterator->_arg + 3);

            find_ns(iterator, oui, subns);

            vnslen = get_unaligned_le16(iterator->_arg + 4);
            
            iterator->_next_ns_data = iterator->_arg + size + vnslen;

            if (!iterator->current_namespace) {
                size += vnslen;
            }
        }



        /*
         * This is what we will return to user, but we need to
         * move on first so next call has something fresh to test
         */
        iterator->this_arg_index = iterator->_arg_index;
        iterator->this_arg = iterator->_arg;
        iterator->this_arg_size = size;


        /* 
         * Internally move on the size of this arg 
         *
         */
        iterator->_arg += size;


        /*
         * Check for insanity where we are given a bitmap that
         * claims to have more arg content than the length of the
         * radiotap section.  We will normally end up equalling this
         * max_length on the last arg, never exceeding it.
         */
        if ((unsigned long)iterator->_arg - (unsigned long)iterator->_rtheader > (unsigned long)iterator->_max_length) {
            return -EINVAL;
        }


        /* 
         * These special ones are valid in each bitmap word 
         */
        switch (iterator->_arg_index % 32) {
            case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
                iterator->_reset_on_ext = 1;

                iterator->is_radiotap_ns = 0;

                /*
                 * If parser didn't register this vendor
                 * namespace with us, allow it to show it
                 * as 'raw. Do do that, set argument index
                 * to vendor namespace.
                 */
                iterator->this_arg_index = IEEE80211_RADIOTAP_VENDOR_NAMESPACE;

                if (!iterator->current_namespace) {
                    hit = 1;
                }

                goto next_entry;
            case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
                iterator->_reset_on_ext = 1;
                iterator->current_namespace = &radiotap_ns;
                iterator->is_radiotap_ns = 1;

                goto next_entry;
            case IEEE80211_RADIOTAP_EXT:
                /*
                 * Bit 31 was set, there is more
                 * 
                 * Move to next u32 bitmap
                 */
                iterator->_bitmap_shifter = get_unaligned_le32(iterator->_next_bitmap);

                iterator->_next_bitmap++;
                
                if (iterator->_reset_on_ext) {
                    iterator->_arg_index = 0;
                } else {
                    iterator->_arg_index++;
                }

                iterator->_reset_on_ext = 0;
                
                break;
            default:
                /* 
                 * We've got a hit! 
                 */
                hit = 1;

            next_entry:
                iterator->_bitmap_shifter >>= 1;
                iterator->_arg_index++;
        }

        /* 
         * If we found a valid arg earlier, return it now 
         */
        if (hit) {
            return 0;
        }
    }
}
